Control system



June 17, 1930 M. ROBISON 1,764,349

CONTROL SYSTEM Filed May 22, 1928 H Forward H49. as

J24 5211 'INVENTOR I 1 v I j Merle Rob/son Patented June 17 1930' UNIT D STATES PATENT OFFICE MERLE BOBISON, O1 DETROIT, MIO'l IIGAN, ASSIONOB TO WESTINGHOUSE ELECTRIC l: MANUFACTURING COMPANY, A CORPORATION 01' PENNSYLVANIA CONTROL SYSTEM Application. filed Kay 22,

The invention relates generally to systems of control and more particularly to control systems for electrically driven vessels, such as ferry boats and the, like.

In operating a ferry boat having a doubleend drive, it is the usual practice to vary the relative operating speeds of the rear and forward driving motors in accordance withthe direction of movement of the boat. Provision is made for operating the rear propeller at a greater speed than the forward pro peller, thereby utilizing the rear propeller to propelthe boat, while the forwardpropeller merely rotates at a predetermined slip 5 speed usually about two-thirds the speed of the rear propeller,. which is the speed that has been found to offer the least resistance to the movementof the boat. Since it is desirable to operate the forward propeller at a lower speed than the driving or rear propel-- ler, provision must be made to change the speed of the particular motor which may be at the forward end of the boat, i. e., the relative speeds of the motors which drive the forward and rear propellers must be changed for every reversal inthe direction of travel of the boat.

It is, therefore, the object of this invention to provide for changing the relative 0 speeds of the driving motors of a ferry-boat in accordance with the change in the direction of movement of the boat. 7 v

A more specific object of the invention is to provide for changing the relative s eeds of the fore and aft driving motors of a erryboat in a predetermined ratio, regardless of the operating speed.

A further object of the invention is to provide for obtaining a desired constant speed ratio of the propeller motors located at the opposite ends of ferry-boats by varying th motor fields.

Another object of the invention is to provide for automatically changing, in one step, the ratio of the speeds of the forward and stern propeller motors of a ferry-boat upon the reversing of the motors to change the direction of movement of the boat.

Other objects of the invention will be emdent from the following description, taken 1928. Serial No. 279,770.

in conjunction with the drawing, in which:

Figure 1 is a diagrammatic view of the main and auxiliary circuits of a ship-propulsion system organized in accordance with the present inventlon;

Fig. 2 is a diagrammatic view of a doubleface place rheostat for controlling the field excitation of the generators inthe system shown in Fig. 1; and

Figs. 3 and 4. are diagrammatic views showing modifications of motor-field-control systems which ma be utilized in a system such as is shown in ig. 1.

Fig. 5 is a modification of the motor-fieldoontrol circuits as shown in Fi 1.

Referring now to Fig. 1 of tie drawing, a double-end-drive ferry-boat is diagrammatically shown in dot-and-dash lines and is provided-with screw propellers 1 and 2 disposed at the opposite ends of the vessel for propelling it in either direction.

The propellers 1 and 2 may be driven by single or double-unit propulsion motors of any suitable type and, as illustrated in this particular embodiment of the invention, direct-current double-unit propulsion motors 3 and 4 are utilized to operate each screw proeller. As shown, themotors in the two doule-units 3 and 4 are provided with armatures 5, 6 and 7, 8, respectively. The armatures are directly connected to their respective propellers and are provided with separately excited shunt fieldlwindings 9, 11 and 12, 13, respectively. A pluralit of variable resistors 14 and 15 are connecte in the fieldexcitation circuits to provideifor controlling the excitation of each driving unit to evenly divide the total load betwe'enthe two armatures of each unit.

The armatures of the motors 3 connected in accordance with the well known Ward-Leonard system of control that is in parallel relation, and disposedto receive ener from a plurality of main generators 16 an d 17 which are preferably connected in series relation.

The main generators may be driven separately or as one unit, by suitable prime movers, such, for example, as internal-combustion engines, steam engines or the like. How

and 4 are ever, in this particular embodiment of the invention, a single prime mover 18 of suitable capacity is utilized fordriving the generators 16 and 17 as a unit.

he main generators 16 and 17 are provided with field windings 21 and 22, respectively, the excitation of whichmay be controlled in any well-known manner to control the voltage developed by the generators, and, in this instance, a reversing-type rheostat is utilized and is shown schematically at 23 in Fig. l.

Excitation current for the field windings of the generators and motors is supplied, in this instance, b constant-potential exciters 24 and 25 provi ed on the main generators 16' and 17. It will be readily understood that, since either exciter may be of a sufficient capacity to supply the whole system, one of the exciters may be used as a spare unit and, therefore, a switch 26 is provided for connecting either exciter to the excitation bus, comprisin line conductors 27 and 28.

The field windings 9, 11 and 12, 13 of the driving units 3 and 4, respectively, are disposed to be energized from the exciter bus conductors 27 and 28 through a plurality of manually operated variable rheostats 31 and 32, as shown.

The operation of the system, when operating in accordance with the present invention, will now be described in detail. In order to provide a source of power for the drivin units 3 and 4, the main generators 16 and 17 may be set in operation by starting the prime (1 mover 18 in the usual manner. stance, the speed and direction of operation of the driving units 3 and 4 is controlled by varying the direction and value of the voltage developed by the main generators by means of the reversing rheostat 23.

It will be observed that the rheostat 23 is constructed in accordance with the wellknown potentiometer principle being provided with a single resistor element 33 and with a plurality of movable contact-makin arms 34 and 35'which are disposed to be moved simultaneously in opposite directions along the resistor element 33.

It will be readily understood that, in the event the contact making arms 34 and 35 are moved from the extreme ends of the resistor In this inunit 33 toward the center, the resistance in series with the generator fields 21 and 22 will be gradually increased until bothcontact-making arms reach the center position, in which case, the voltage impressed upon the generator fields b quently, the voltage developed by the main generators 16 and 17 is reduced to substantially zero value, depending upon the strength magnetism. Further movement of the contact-making arms34 and 35 in the same direction of travel causes a reversal in the direction of the exciting curg respectively, are connected g ators from a maximum ecomes zero and, conseb rentafter the mid-point of the resistor element 33 has been passed, which dissipates the residual magnetism of. the generator fields and gradually increases the voltage to a maximum in the opposite direction when the extreme ends of the resistor element 33 are again reached.

A preferred form of a reversing rheostat of this type is shown in Fig. 2 and like reference numerals are utilized to designate similar parts in Figs. 1 and 2. In Fig. 2 it will be observed that the rheostat is provided with a plurality of face plates 36 and 37 each having the usual arrangement of contact buttons designated as A to K and A to K, inelusive, in addition to the contact-making arms 34 and 35. In order to provide for moving the contact-making arms 34 and 35 simultaneously, they are disposed to be actuated by means of a shaft 41 extending between the two face plates 36 and 37 and dis posed for operation by any suitable type of control mechanism, such, for example, as a pilot-house controller, or the like (not shown) such as are well known in the art.

It will be observed that the first contact button A, on the face plate 36 is connected to one end of the resistor element 33, while the first contact button A of the face plate 37 is connected to the opposite end of the resistor element, and, likewise, the last contact buttons K and K on the face plates 36 and 37, to opposite ends of the resistor element 33 in the reverse orer, thereby providing the same arrangement as shown schematically in Fig. 1. The intermediate contact buttons between those designated as A and K of each of the face plates are connected at common points and at predetermined intervals on the resistor element 33 in such manner that simultaneous movement of the contact-making arms 34 and 35 eflects an equal variation of the field resistance of the generator fields, thereby changing the field excitation of the genervalue in one direction, to a maximum value in the opposite direction:

It will be observed that the contact buttons F and F are connected to the mid-point of the resistor element 33, thereby making this position of the contact-making arms the off position in respect to the operation of the driving units 3 and 4, since, in this position, the voltage developed by the main generators 16 and '17 is of zero value.

Assuming that it is desired to operate the oat in the direction indicated by the arrow in Fig. 1, the control mechanism (not shown) is operated, as. hereinafter described, to move the contact-making arms 34 and 35 simultaneously from the center or off position towards the extreme ends of the resistor element 33. In this event, the main generators l6 and 17 develop a voltage in 1.

direction determinedby the direction of flow of the excitin current in the generator fields 21 and 22. inee the driving units 3 and 4 are connected for energization from the generators, as hereinbefore described, they now operate to drive the boat in the direction indicated by the arrow at the right of Fig. 1.

Since the propeller 2 is in the forward end of the boat, as it moves to the right, its

operating speed must be so regulated as to reduce its resistance to the movement'of the vessel to a minimum and, as hereinbefore described, this operating or slip speed of the forward propeller 2 is approximately of the speed of the rear propeller 1.

In order to establish the desired ratio between the relative speeds of the forward and rear propellers, provision is made for automatically controlling the excitation of respective driving units simultaneously with the operation of thereversing rheostat 23. It will be observed that the rheostat 31 is provided with a plurality of resistor elements 42 and 43 which may be in the form of manually-operated field rheostats connected in parallel relation to each other and in series relation to the motor-field windings 9 and 11. Likewise; the rheostat 32 for controlling the excitation of the driving unit 4 is provided with a similar arrangement of variable resistor elements 44 and 45.

It will be readily understood that, by utilizing only one resistor such, for example, as 42, in the motor excitation circuit, that a certain value of field current may be ob tained and that, by connecting the second resistor 43 in parallel relation to the first and maintaining the same value of exciter voltage, the resistance or the field circuit of the motor 3 may be decreased and, consequently, the excitation current flowing in the motor field circuit may be changed or increased to a certain .predetermined value in a one-step operation, to give the desired speed ratio between the propellers.

In order to control the change in excitation of either of the main driving units 3 and 4 in accordance with the direction of movement of the vessel, a plurality of switches 46 and 47 for connecting the resistors 43 and 44 in their respective field circuits are utilized and disposed to be controlled in accordance with the operation of the reversing rheostat Referring to Fig. 2, it will be observed that the face plate 36 is provided with a pair of semicircular contact segments 48 and 49 which are disposed to be engaged by an ex tension member 51 of the contactanaking arm 34 when in any of its operating positions, except in the central position, engaging the contact button F. A second circular contact segment 52 is also provided on the face plate 36 and disposed to be engaged by the extension member 51 in all its operating positions .to complete an operating circuit for either of the resistor-controlling switches 46 and 47, depending upon the operatingv osition of the contact-making arm 34. en the contact-making arm 34 is in the position shown, an operating circuit is established for the resistor-controlling switch 46 which extends from one side of the exciter bus, through conductor 53, operating coil of the syvitch 46, conductor 54, segments 49 and 52, brldged by the arm extension 51, and conductor 55, to the other side of the exciter bus. However, in this instance, in order to reduce the speed'of the forward propeller 2, the field excitation of the driving unit 4 is increased to a predetermined degree by causing the operation of the resistor-control switch 47. This occurs upon movement of the contact-making arms 34 and 35, as shown in Fig. 2, to the full position in the forward direction where they engage contact buttons K and K, respectively. In this instance, the contact segments 48 and 52 are bridged by the arm extension 51, and an operating circuit is established for the resistor-control switch 47.

It will be readily understood that an alternate method of controlling the connection of the resistors 43 and 45 may be employed, as shown in Fig. 5. This scheme provides for eliminating the resistor-control switches 46 and 47 by utilizing the contact segments 48, 49 and 52 on the face plate 36 for conmeeting the resistors in the motor-field circuits instead of for controlling the operating circuits for the resistor-control switches 46 and 47. As shown in Fig. 5, the outer contact regment 52, as illustrated in Fig. 2, is constructed in two parts 52a and 525, which are paired with the contact segments 48 and 49, respectively; The contact segments of each pair are disposed to be bridged by the extension member 51, thereby functioning as switches to make the connection of their associated resistors in the motor-field circuits in response to the operations of the reversing rheostat 23.

In order to regulate the system to obtain the desired ratio between the relative operating speeds of the forward and rear driving units, the resistors 44 and 42 are first adjusted with the resistors-45 and 43 excluded from the field circuit, to obtain the desired amount of excitation for high-speed operation and then the resistors 45 and 43 are connected in parallel to the resistors 44 and 42 and their resistance value varied until the desired amount of excitation is obtained for slow-speed operation.

It will.be readily understood that, by uti if necessary, any desired adjustment may be made while the system is in operation. Furthermore, the maximum and minimum ex-' citation is always maintained at the same values and, therefore, the same speed of operation of the driving units is always obtained for equal values of generator voltage impressed thereon.

Without further explanation, it will be appreciated that a similar operation takes place upon the reversal of the direction of movement of the vessel; in which case, the propeller l is operating in the forward position and, therefore, the switch 46 is energized to connect the resistor 43 in the field circuit of the driving unit 3 in the manner described hereinbefore in connection with the operation of the driving unit 4.

Figs. 3 and 4 show alternative arrangments' of resistors for so controlling the motor fields as to reduce the amount of resistance required by utilizing a single resistorfor both the high and low-speed operation, or else a plurality of resistors connected in series relation.

It may be stated in conclusion that, while the illustrated example constitutes a practical embodiment of my invention, I do not Wish to limit myself strictly to the exact details herein illustrated, since modifications 0f the same may be made without departing from the spirit of the invention, as defined in the appended claims.

claim as my invention:

1. In a ship-propulsion system, in combination, a propeller located at each end of the ship, motors for driving the propellers, means for supplying power to the motors, meansfor controlling the power supplied to the motors to change their speed and direction of operation, and means disposed to change the relative speeds of the motors a predetermined amount, said means being responsive to the initial operation of the powercontrolling means, and auxiliary means disposed to vary the degree of relative speed change independently of the controller operation.

2. In a ship-propulsion system, in combination, a propeller located at each end of the ship, motors for driving the propellers, means for supplying power to the motors, means for controlling the power supplied to the motors, lneans disposed to change the relative speeds of the motors a predetermined amount in one step in response to the operation of the power-controlling means and means for varying the degree of the relative speed change independently of the last named means.

3. In a ship-propulsion system, in combination, a propeller located at each end of the ship, motors for driving the propellers at different speeds, a source of power for the motors, and means for controlling the operation of the motors, said means Comprising manually operable means and auxiliary means operated in accordance with said manually operable means for simultaneously controlling the direction of operation of the motors and for efiecting a change of speed between the motors at the respective ends of the ship to establish a fixed speed ratio when ever a change in the direction of operation of the ship is caused to occur, and means associated with each motor for varying the Speed ratio while the motors are in operation.

4. In a ship-propulsion system, in combi-. nation, a propeller located at each end of the ship, motors for driving the propellers, means for supplying power at the same voltage to the motors, means for simultaneously varying the voltage supplied to each motor to vary the speed of the motors, means for changing the excitation of either of the motors in a one step operation to change their relative speeds regardless of the impressed voltage, means carried by, and disposed to operate in conjunction with, said voltage-varying means for controlling the operation of the means for changing the motor excitation, and auxiliary-excitationcontrolling means associated with each motor for further varying the excitation of the motors.

5. In a ship-propulsion system, in combination, a propeller located at each end of the ship, motors for driving the propellers having separately excited field windings, a source of power for the motors, means for controlling the voltage of the power source to simultaneously vary the motor speeds. said means being disposed to reverse the current supplied from the power source to effect the reverse operation of the motors, means for changing the relative speeds of the motors, said means comprising a plurality of variable resistors connected in the motor fields, and means disposed for operation in accordance with the said voltage-control means for alternately changing in a one step operation the effective amount of resistance in the field circuits, said variable resistors being operable to vary the speed relation of the motors independently of the speed chan ing means. I

6. n a ship-propulsion system, in combination, a driving system comprising a plurality of independent driving units and means for sup lying power to the driving units, means or controlling the direction and speed of the operation in conjunction with the direction and speed-controlling means for causing the relative speeds of the said units to be in a fixed ratio for all operating speeds of the system in either direction, and manuallyoperable means for individually varying the speed of each driving unit to provide for obtaining different speed ratios.

7. In a ship-propulsion system, in combinasystem, means disposed for tion, a plurality of propellers, a plurality of -parallel-connected motors for driving the propellers at different speeds, means for controlling the direction of operation of the motors, means disposed for operation in response to the o eration of said direction-controlling means or alternately changing'the ratio of the operatingspeeds of the motors, and independently operable means for establishing different speed ratios. i

8. In a ship-propulsion system, in combination, a propeller located at each end of the ship, a plurality of drivin units for operating the propellers, means for simultaneously controlling the direction and speed of movements of all of said driving units, means for causing the relative speeds of the driving units to be maintained at a predetermined fixed ratio at all speeds of said units, and means for changing the ratio while the driving units are in operation.

9; In a ship-propulsion system, in combination, a propeller located at each end of the ship. a plurality of drivin units for operating the propellers, means tor simultaneously controllin the direction and sp causing the relative speeds of the driving units to be maintained at a redetermined fixed ratio at all speeds of said units when operating in one direction, and means for c anging the ratio while the driving'units,v

are operating in either direction.

10. In a ship-propulsion system, in combination, a propeller located at each end of the ship, a plurality of driving units for operating the propellers, means comprising a source of power and a controller for simultaneously controlling the direction and speed of movement of all of said driving units, and means comprising a single controller for causing the relative speeds of the drivin units to be maintained at a prcdetermine fixed ratio at all speeds of said units when operating in one direction and for causing the speeds of the eed of move-. ment oi a l of said driving units, means for 13. In a propulsion system for ships, in

combination, a pluralityof propeller screws for propelling the shi in either direction,

motor units for each 0 the propeller screws, a power source for the motor units, a controller for operating the motor units at predetermined speeds in either direction, and means cooperative with the controller for controlling the field excitation of the motors to establish a predetermined speed ratio between said motors and to maintain the maximum and minimum speeds the same for either direction of movement. L

14. In a ship-propulsion system, in combination, a propeller located at each end of the ship, motors for actuating the propellers, means for controlling the speed and direction of operation of the motors, means disposed to vary the relative degrees of excitation of the motors, said means being responsive to a predetermined degree of operation of the speed and direction-controlling means, and means independently operable for changing the ratio of field excitation between the motors irrespective of the operation of the means for controlling the speed and direction of operation of the motors.

controlling the excitation of the In testimony whereof, I have hereunto sub scribed my name 1928. p

units to be in the reciprocal of said ratio when operating in the opposite direction.

11. In'a ship-propulsion system, in combination, a propeller provided at each end of the ship, motors for driving the'propellers, said motors being provided yvith separately excited field windings, means for controlling the speed and direction of operation of the motors simultaneously and means for independently controlling the excitation of the motors at each end of the ship, said means comprising a variable resistor normally in series with the field winding and a second resistor disposed to be connected in parallel 12. In a ship-propulslon system, in combination, apropeller provided at each end of the ship, motors for driving the propellers, said motors bein provided with separately excited field win ings, means for controlling 

